1. Field of the Invention
The present invention relates to a multi-function image processing system having a function as a printer for printing letters from an external host computer or the like and a function as a facsimile (hereinafter referred to as the "fax") for transmitting and receiving data using a communication line.
2. Description of the Related Art
In recent years, the use of what is called a multi-function image processing system capable of performing a variety of functions has extended in place of stand-alone equipment such as faxes, printers and copiers for saving required space and reducing total cost.
A multi-function image processing system with dual functions of fax and printer has been developed, in which a conventional fax having a scanner function is combined with a printer having an interface with a host computer. This system can thus realize copying and scanning functions as well as functions of a fax and a printer.
A conventional multi-function image processing system will be described. FIG. 10 is a block diagram showing a conventional multi-function image processing system configured on the basis of a fax and a printer. Reference numeral 21 designates a conventional multi-function system comprising three main parts including a print engine 9, a fax control unit 22 and a printer control unit 23.
Further, numeral 2 designates a host computer for issuing a command for execution of application software or data processing. The host computer 2 transmits print data to the multi-function system 21. Also, numeral 25 designates a print engine controller functioning as a control interface between the print engine 9 and the printer control unit 23.
In the fax control unit 22, numeral 3 designates a public line for transmitting and receiving data to and from a remote terminal, numeral 4 a channel controller for controlling the interface with the public line 3, and numeral 5 a reader for scanning an original and converting it into image data. Numeral 6 designates a fax controller for controlling the conversion of an original into an electrical signal at the reader 5, processing the data transmitted to and received from the public line 3, converting the data received from the public line 3 into fax print data or otherwise controlling the whole operation of the fax control unit 22.
In the printer control unit 23, numeral 7 designates a host interface for transmitting and receiving data to and from the host computer 2, numeral 8 a print data processing section, and numeral 24 a print engine interface. The print data processing section 8, which processes the data received from the host computer 2 and produces print data, also transmits the print data through the print engine interface 24 to the print engine controller 25 and thereby controls the whole operation of the print control unit 23. Numeral 26 designates a printer-fax interface, through which data are transmitted and received between the printer control unit 23 and the fax control unit 22.
Explanation will be made about the operation of the conventional multi-function image processing system configured as described above. First, data to be printed sent from the host computer 2 are received through the host interface 7. The print data processing section 8 produces print data on the basis of the received data.
Then, when the print data are prepared, the print data processing section 8 generates a print request signal to the print engine controller 25 through the print engine interface 24, thereby making a print request. Then, the print engine 9 performs a predetermined printing operation in accordance with the print request if it is ready for printing. A vertical sync signal (hereinafter referred to as the "TOP signal") and a horizontal sync signal (hereinafter referred to as the "HSYNC signal") for synchronizing the printing operation are applied to the printer control unit 23. The print data processing section 8 sends the print data to the print engine controller 25 based on the TOP signal and the HSYNC signal, with the result that the printing operation is performed by the print engine 9.
The data received by the fax control unit 22 through the channel controller 4 from the public line 3 are processed by the fax controller 6. Fax print data are produced on the basis of the data thus processed. Upon preparation of the fax print data, the fax controller 6, which is not directly connected with the print engine controller 25, communicates with the print data processing section 8 of the printer control unit 23 through the printer interface 26. In response to this communication, the printer control unit 23 communicates with the print engine controller 25, so that a print request signal representing a print request is applied to the print engine 9.
As far as the print engine 9 is ready for printing operation in the meantime, a predetermined printing operation is performed by the print engine 9 in accordance with the print request. The TOP signal and the HSYNC signal are then applied to the print data processing section 8 from the print engine 9 through the print engine controller 25 and the print engine interface 24. The fax control unit 22 transfers the fax print data to the printer control unit 23 through the printer fax interface 26 in advance. The print data processing section 8 transfers the print data to the print engine controller 25 on the basis of the TOP signal and the HSYNC signal, so that the print data are sent to the print engine 9, thereby executing the printing operation.
In the above-mentioned conventional configuration, however, the print engine interface 24 for transmitting and receiving data to and from the print engine controller 25 is provided on only a selected one of the fax control unit 22 and the printer control unit 23. In fact, the print engine interface 24 is provided only on the printer control unit 23 in the conventional system under consideration.
In the case where the fax control unit 22 prints an image on the basis of the print data received from the public line 3, therefore, communication is necessary beforehand with the print engine 9 through the printer control unit 23. If data are sent from the host computer 2 to the printer control unit 23 during the communication between the fax control unit 22 and the print engine 9, the printer control unit 23 is incapable of receiving the data, and the rejection of a print request is displayed on the display unit of the host computer 2. The host computer 2 therefore cannot transfer to the next task during the printing operation.
Also, the configuration in which the printer-fax interface 26 is interposed between the fax control unit 22 and the printer control unit 23 requires hardware such as a bidirectional port or a memory shared by the two controllers. The result is a complicated control operation and an increased processing time, thereby leading to the problem of an increased system cost.